1. Field of the Invention
The present invention relates to a liquid crystal display device capable of providing bright display without using a polarizing plate, and more particularly to a liquid crystal display device capable of providing desired display by contrast between a color filter film applied to a substrate and a liquid crystal material doped with dichroic dyes.
2. Description of the Related Art
A liquid crystal display device has such a structure as seen from the general structure of a transmission type liquid crystal display panel shown in FIG. 8. Specifically, as seen from FIG. 8, electrode patterns 3 and 4 are formed on the surfaces of insulating substrates 1 and 2, and orienting films 5 and 6 are formed thereon. The two insulating substrates 1 and 2 are bonded to each other on their peripheries by a sealant 7 with a prescribed gap of a spacer (not shown) therebetween. The liquid crystal is injected into the gap to constitute a liquid crystal layer 8. On the outsides of the insulating substrates 1 and 2, polarizing plates 9 and 10 are provided. In this way, a liquid crystal display panel 11 is formed.
On the rear side of the liquid crystal panel 11 which is opposite to a viewer, a back light 13 such as a bulb, a fluorescent lamp, etc. is arranged through an optical diffusing plate 12. With respect to the light from the back light 13, only linear polarized light of natural light in a certain vibrating direction can be transmitted by means of the polarizing plate 9 on the rear side. According to whether or not a voltage is applied to the liquid crystal layer, the light travels with the vibrating direction twisted or travels straight as it is with the vibration direction not twisted. Whether or not the light is transmitted can be controlled by the absorption axis of the polarizing plate 10 on the front side which is a viewer side to provide a desired display.
As described above, the conventional liquid crystal display device uses the polarizing plates to adopt only the light vibrating in a certain direction of natural light. Therefore, most of the light is interrupted by the polarizing plate so that unless a bright back-light is used, bright display cannot be realized. However, use of the bright back-light excessively consumes a battery in a liquid crystal display device such as a portable appliance which is driven by the battery. This applies to a reflection type liquid crystal display device in which light is caused to be incident from the viewer side to use the reflected light. Namely, in the reflection type liquid crystal display device, a bright image can be obtained only in a bright place.
In addition, the polarizing plate is very expensive to increase the production cost of the liquid crystal display device. This provides a limit of cost reduction in the LC device which is used in an inexpensive electronic appliance such as a portable appliance. The present invention has been accomplished in order to solve such a problem.
An object of the present invention is to provide a liquid crystal display device capable of providing bright display without using polarizing plates and can be manufactured at low cost.
In order to attain the above object, in accordance with a first aspect of the present invention, there is provided a liquid crystal display device comprising: first and second substrates with electrode patterns formed thereon on a front side and rear side of the device, which are bonded to each other on their peripheries by a sealant with a prescribed gap therebetween; a liquid crystal material doped with dichroic dyes injected into the gap to constitute a liquid crystal layer; a first color filter film with a prescribed color provided at an area where the electrode pattern is not provided on the first substrate on the front side; and a second color filter film with the same color as the prescribed color at at least an area where the electrode pattern is not provided on the second substrate on the rear side,.
In the present invention, the first substrate on the front side refers to a substrate on the side of a viewer when he sees the liquid crystal display device. The second substrate on the rear side refers to another substrate on the side (background) far from the viewer. Further, the color filter film with a prescribed color refers to a color filter of the background of the liquid crystal display device, which may provide a whitish background such as transmitted white light by printing e.g. white ink and yellow ink. The color filter film may be provided not on the side of the liquid crystal layer of the substrate, but may be provided on the side opposite to the liquid crystal layer.
In the above configuration, an area where the electrode pattern is not provided on the first substrate on the front side is viewed as the color, e.g. white of the color filter on the front side. As for the area where the electrode pattern is provided on the first substrate on the front side, the portion with a voltage applied between itself and an opposite electrode, where liquid crystal molecules rise, appears as the color of the color filter applied to the surface of the electrode pattern on the second substrate on the rear side. The portion with a voltage not applied between itself and an opposite electrode appears as the color (e.g. black) of the dichroic dyes added to the liquid crystal. Thus, by controlling the application of a voltage, a desired display in e.g. black can be made on a white background.
In accordance with the present invention, a desired display can be realized by voltage control without using a polarizing plate so that a very bright display screen can be obtained. Therefore, the liquid crystal display device according to the present invention can be applied to a transmission type liquid crystal display device such as a portable appliance or a reflection type liquid crystal display device which can be used in a dim place. The present invention, in which no polarizing plate is used, can be realized at low cost, thus contributing the cost reduction of an electronic appliance using the liquid crystal display device.
A second aspect of the device is a liquid crystal display device according to the first aspect, wherein said first substrate comprises a light-permeable substrate; a light-permeable electrode pattern formed on an internal surface of said light-permeable substrate so as to correspond to a light emitting segment; a first color filter film formed at an area where the light-permeable electrode pattern is not provided; and an orienting film formed to cover the entire surface of the first substrate.
A third aspect of the device is a liquid crystal display device according to the first aspect, wherein said second substrate comprises a substrate, an electrode pattern formed on an internal surface of said substrate so as to correspond to a light emitting segment, a second color filter film with the same color as the prescribed color stacked on the electrode pattern so as to have the same pattern as that of the electrode pattern, and an orienting film formed to cover the entire surface of the second substrate.
A fourth aspect of the device is a liquid crystal display device according to the first aspect, wherein said first substrate comprises a light-permeable electrode pattern formed on an internal surface of a light-permeable substrate so as to correspond to a light emitting segment; an orienting film formed thereon and a first color filter film on an outer surface of said light-permeable substrate formed at an area where the light-permeable electrode pattern is not provided; and an orienting film formed to cover entirety of the first substrate.
A fifth aspect of the device is a liquid crystal display device according to the first aspect, wherein said second substrate comprises a substrate; an electrode pattern formed on an internal surface of said substrate so as to correspond to a light emitting segment; an orienting film formed thereon; and a second color filter film with the same color as the prescribed color on the outer surface of the substrate so as to have the same pattern as that of the electrode pattern.
A sixth aspect of the device is a liquid crystal display device according to the first aspect, wherein said second substrate comprises a substrate; an electrode pattern formed on an internal surface of said substrate so as to correspond to a light emitting segment; a second color filter film with the same color as the prescribed color stacked on said electrode pattern to cover the entire surface of the substrate; and an orienting film formed thereon.
A seventh aspect of the device is a liquid crystal display device according to the first aspect, wherein said second substrate comprises a substrate; an electrode pattern formed on an internal surface of said substrate so as to correspond to a light emitting segment; an orienting film formed thereon; and a second color filter film with the same color as the prescribed color formed so as to cover the entire outer surface of said substrate.
An eighth aspect of the device is a liquid crystal display device according to the first aspect, wherein said second substrate comprises a substrate; an electrode pattern formed on an internal surface of said substrate so as to correspond to a light emitting segment; a second color filter film with the same color as the prescribed color formed so as to cover the entire outer surface of said substrate and an orienting film formed thereon.
A ninth aspect of the device is a liquid crystal display device according to the first aspect, wherein said second substrate comprises a color substrate with the same color as said prescribed color; and an electrode pattern formed on an internal surface of said substrate so as to correspond to a light emitting segment.
A tenth aspect of the method is a method of manufacturing a liquid crystal display device which comprises the steps of:
forming a first substrate composed of a light-permeable electrode pattern formed an internal surface of a light-permeable substrate so as to correspond to a light emitting segment and a first color filter film with a prescribed color formed at an area where the light permeable electrode pattern is not provided;
forming a second substrate includes a substrate, an electrode pattern formed on an internal surface of a substrate so as to correspond to the light emitting segment and a second color filter film with the same color as the prescribed color stacked on the electrode pattern so as to have the same pattern as that of the electrode pattern;
bonding said first and said second substrate to each other on their peripheries by a sealant with a prescribed gap between the opposite electrode patterns; and
injecting a liquid crystal material doped with dichroic dyes into the gap.
An eleventh aspect of the method is a method of manufacturing a liquid crystal display according to the tenth aspect, wherein said step of forming the first substrate comprises the steps of:
forming a transparent conductive film on the internal surface of said light-permeable substrate;
patterning said transparent conductive film using a first resist pattern formed by photolithography as a mask to provide the electrode pattern; and
forming the first color filter film on the entire resultant surface with said first resist pattern being left;
removing said first resist pattern by the lift-off technique to leave said first color filter film only an area where the electrode pattern is not provided.
A twelfth aspect of the method is a method of manufacturing a liquid crystal display according to the tenth aspect, wherein said step of forming said second substrate comprises the steps of:
successively stacking a conductive film and the second color filter film on the surface of the substrate; and
patterning said conductive film and second color filter film formed by photolithography using a second resist pattern as a mask.
A thirteenth aspect of the method is a method of manufacturing a liquid crystal display according to the tenth aspect, wherein said step of forming said first substrate comprises:
forming a transparent conductive film on the surface of the light-permeable substrate;
applying a photoresist on said transparent conductive film;
forming the first color filter film of photosensitive resin of an inverted type of the photoresist on a rear side of said transparent substrate; and
irradiating the photoresist with light having a wavelength making said photosensitive resin photosensitive so that said transparent conductive film and said photosensitive resin are patterned to have the same pattern.
The above and other objects and features of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings.